De Lacey Antonio L, Stadler Christian, Fernandez Victor M, Hatchikian E Claude, Fan Hua-Jun, Li Shuhua, Hall Michael B
Instituto de Catalisis, CSIC, Campus Universidad Autonoma-Cantoblanco, Madrid 28049, Spain.
J Biol Inorg Chem. 2002 Mar;7(3):318-26. doi: 10.1007/s00775-001-0301-7. Epub 2001 Oct 20.
The binding of carbon monoxide, a competitive inhibitor of many hydrogenases, to the active site of Desulfovibrio fructosovorans hydrogenase has been studied by infrared spectroscopy in a spectroelectrochemical cell. Direct evidence has been obtained of which redox states of the enzyme can bind extrinsic CO. Redox states A, B and SU do not bind extrinsic CO; only after reductive activation of the hydrogenase can CO bind to the active site. Two states with bound extrinsic CO can be distinguished by FTIR. These two states are in redox equilibrium and are most probably due to different oxidation states of the proximal 4Fe-4S cluster. Vibrational frequencies and theoretical quantum mechanics studies (DFT) of this process preclude the possibility of strong bonding of extrinsic CO to the Fe or Ni atoms of the active site. We propose that CO inhibition is caused by weak interaction of the extrinsic ligand with the Ni atom, blocking electron and proton transfer at the active site. A calculated structure with a weakly bound extrinsic CO at Ni has relative CO frequencies in excellent agreement with the experimental ones.
一氧化碳是许多氢化酶的竞争性抑制剂，利用光谱电化学池中的红外光谱研究了一氧化碳与果糖脱硫弧菌氢化酶活性位点的结合情况。已获得直接证据，证明该酶的哪些氧化还原状态能够结合外部一氧化碳。氧化还原状态A、B和SU不结合外部一氧化碳；只有在氢化酶经还原激活后，一氧化碳才能结合到活性位点。通过傅里叶变换红外光谱（FTIR）可以区分两种结合了外部一氧化碳的状态。这两种状态处于氧化还原平衡，很可能是由于近端4Fe-4S簇的不同氧化态所致。该过程的振动频率和理论量子力学研究（密度泛函理论，DFT）排除了外部一氧化碳与活性位点的铁或镍原子形成强键的可能性。我们认为，一氧化碳抑制是由于外部配体与镍原子的弱相互作用，从而阻断了活性位点的电子和质子转移。计算得出的镍原子上弱结合外部一氧化碳的结构，其一氧化碳相关频率与实验结果非常吻合。
